"When you examine this, it becomes devilishly complicated. Nobody expects this to be without complication.

"Let's wait and see - there is a huge reservoir of goodwill for the UK within this organisation.

"There are countries that have traded with Britain for decades, if not centuries.

"But they are trade negotiators and they are looking out for the best interests of their people."

Representing the UK in those talks will be Julian Braithwaite, the ambassador and permanent representative to no fewer than 37 organisations in Geneva - including the WTO.

When he came to Geneva four years ago, the WTO took up a small fraction of his time - after Brexit it will be his focus.

He told me that he still hoped that the government would achieve its withdrawal agreement, but conceded that his team had worked on contingency plans for everything from joining a customs union all the way through to Britain leaving without a deal on 29 March.

And it is the prospect of a no-deal Brexit that increasingly preoccupies him, and many others at the WTO.

"The sort of issues we're look at is how could we use the power we would have in the WTO to regulate our tariffs to minimise impact on consumers, supply chains and mitigate implications of leaving the EU without a deal - those are the sort of issues that are being considered," he said.

Tariffs are discussed constantly in Geneva.

Image:Julian Braithwaite, UK permanent representative at WTO, is increasingly pre-occupied by the prospect of a no-deal Brexit

Each member country has a huge document, known as a schedule, that details the tax that will be charged on products that are exported between one nation and another.

The WTO's members agree a maximum rate, and individual countries can impose a lower rate if they wish.

British trade negotiators have spent months preparing a bespoke set of tariffs that the UK would use after Brexit, largely based upon the existing schedule inherited from the European Union.

Sky News understands that the UK's proposals are likely to be presented in the coming weeks.

Senior Brexiteers, including the International Trade Secretary Liam Fox, nd the former Brexit Secretary David Davis, have flagged the possibility of reducing some tariffs to zero in order to cut the price of imports and stimulate the economy.

It's a suggestion that has been met by some raised eyebrows here in Geneva.

Dimitry Grozoubinski, a former trade negotiator for the Australian government, told Sky News that such a move "will have very real winners and losers".

He told me: "Under WTO rules you can't just reduce tariffs to help the European Union in the absence of a free trade, you have to throw open the doors to everyone.

"Are the UK public and business really prepared to compete, one-on-one, with Chinese manufacturing, or US agriculture, or Australian beef and lamb?